Abstract
Background:
Low birth weight (LBW) significantly impacts children’s development and long-term health, with maternal anaemia being a key predictor. While the direct association between anaemia and LBW is well-documented, its effects at different pregnancy stages remain uncertain. This study aims to explore how changes in hemoglobin concentration across the pregnancy trimesters impact birthweight compared to absolute hemoglobin levels in mothers.
Methodology:
This secondary data analysis explores comprehensive antenatal histories, physical examination details, and hemoglobin levels of 226 mothers till delivery, in the rural field practice area of a tertiary care institute, where mothers attended monthly antenatal care (ANC) clinics at rural subcenters. The study included only those pregnant women who completed ANC check-ups from the first trimester through delivery, comparing changes in maternal hemoglobin across trimesters and the birth weights of newborns.
Results:
Out of 226 deliveries, 46 resulted in LBW babies. Changes in hemoglobin concentration from the first to the third trimester and from the second to the third trimester had a statistically significant influence on birth weight. In contrast, the severity of anaemia in different trimesters did not show a significant association with birth weight.
Conclusion:
Changes in hemoglobin levels, rather than absolute hemoglobin levels, may play a significant role in determining the birth weight of newborns. This finding could inform treatment strategies and expected outcomes. Further research is needed to explore the plausibility of this hypothesis and its underlying biological mechanisms.
Keywords: Antenatal care, birth weight, hemoglobin changes, maternal anemia, newborn
INTRODUCTION
Low birth weight (LBW), defined as a birth weight of less than 2.5 kg, is a prevalent global maternal and child health problem, affecting 15-20% of all births worldwide.[1] LBW babies face an increased risk of adverse outcomes across perinatal, childhood, and adult stages.[2] Maternal anaemia is a significant predictor that impacts foetal growth and neonatal outcomes.[3] In India, where anaemia among pregnant women remains a longstanding public health problem, the risk of LBW babies is notably high.[4] This poses substantial logistical challenges, prompting the country to implement a test-and-treat approach under the Anaemia Mukt Bharat program.[4]
Current research predominantly focuses on absolute hemoglobin values and anemia severity across different trimesters in relation to neonatal outcomes. Maternal anaemia has been shown to affect placental vascularization by modulating angiogenesis early in pregnancy, which highlights the placenta’s adaptability to optimize fetal growth and viability.[5] Some studies suggest that changes in hemoglobin (Hb) levels from early pregnancy to delivery, rather than absolute levels alone, may impact birth outcomes.[6] Additionally, a late rise in hemoglobin has been associated with adverse effects on birth weight.[7] However, the specific impact of absolute hemoglobin levels versus changes in maternal hemoglobin concentration throughout pregnancy on birth weight remains unclear. Thus, exploring the influence of hemoglobin concentration changes at various stages of pregnancy and comparing these effects with absolute hemoglobin levels could offer valuable insights for tailoring protocols as well as programmatic approaches. This study investigates the impact of changes in maternal hemoglobin levels across pregnancy trimesters on birth weight.
METHODS
The current study is a secondary data analysis conducted within the framework of regular antenatal care (ANC) clinics held monthly at subcenters affiliated with the rural field practice area of the Department of Community Medicine and Family Medicine (CM and FM) in a tertiary care hospital in Eastern India. This rural field practice area includes a Primary Health Centre (PHC) and 10 subcenters, located approximately 86 km from Kolkata and 36 km from the institute. The PHC serves 29 villages with a population of 60,000 (according to the 2011 census). Outreach healthcare services at the subcenters, including various specialty clinics such as ANC and noncommunicable diseases (NCD), commenced in April 2021. ANC clinics at these subcenters are managed by a team consisting of faculty, senior residents, medical social workers (MSWs), and laboratory personnel.
Quality of data collected
For each maternal visit, comprehensive documentation is performed using a prestructured format, including maternal history, general and abdominal examinations, and essential investigations such as blood grouping, blood glucose assessment, urine dipstick tests, and hemoglobin estimation using the HemoCue301. A unique number is allotted to each antenatal case and the obstetric examination of each subsequent visit is recorded in the same format. These records are entered into MS Excel and maintained by the department.
The study population comprised pregnant women residing in the rural field practice area of the Department of Community and Family Medicine at the tertiary care institute in Eastern India who attended ANC clinics from the initial trimester through delivery. As a record-based study, inclusion criteria were completed ANC visit records, at least one consultation in each trimester, and comprehensive entries covering sociodemographic details, past medical and surgical history, general and abdominal examination specifics, and Hb concentration across all trimesters along with documented pregnancy outcomes. Exclusion criteria included twin pregnancies, abortions, preterm deliveries, or pre-existing medical conditions such as hypertension, diabetes mellitus, thyroid disorders, asthma, tuberculosis, HIV-positive status, and other serological infections. Birth outcomes and newborn birth weight were obtained from ANC, and birth registers maintained by the Auxiliary Nurse Midwife (ANM) and Accredited Social Health Activist (ASHA) at the subcenters.
Weight gain during pregnancy was calculated from the mother’s weight at the first clinic visit, with weight recorded at each visit. Weight gain during each trimester was classified operationally based on previous studies.[8] The primary outcome assessed was the birth weight of the newborn. Given the mean birth weight of newborns in West Bengal is 2939 g, with a standard deviation of 0.321[9] and an expected 75 g lower birth weight for newborns of anemic mothers compared to nonanemic mothers[10] (at least 2.5% of the mean birth weight), the final sample size required was 251. Data on birth outcomes were collected from records maintained in the ANC register at the subcenters, with entries completed by the ANM. Data collection included records of mothers with anticipated delivery dates on or before December 31, 2022, since the inception of the ANC clinic. Therefore, the study included comprehensive records of pregnant women who completed the recommended four antenatal checks from the first trimester through delivery between April 2021 and December 2022.
Ethical approval was obtained from the Institute Ethics Committee (IEC) (ref no. IEC/AIIMS/Kalyani/2022-003).
Data was analyzed using SPSS version 21. Chi-square test was applied to check the differences between the low birth weight and normal birth weight babies with respect to the various sociodemographic and obstetric variables. Differences in continuous variables between low birth weight and normal birth weight newborns were compared using a t-test. A P-alue of <0.05 was considered to be statistically significant.
RESULTS
A total of 363 deliveries occurred during the study period out of which 226 records of pregnant women were found to be complete and considered for final analysis. The mean age of mothers was 24.0 ± 4.4 years, and that of their husbands was 30.8 ± 5.1 years. Almost half of the participants (46.0%) and their husbands (39.8%) had completed secondary education. The mean change in hemoglobin from the first to the third trimester was − 0.8 ± 1.3 g/dL. In the first trimester, the average weight of mothers was 50.3 ± 9.3 kg. There was a mean weight gain of 7.5 ± 3.3 kg through the entire pregnancy. The average birth weight of the infants was 2.7 ± 0.4 kg. Only a third of the deliveries (31.4%) were normal vaginal deliveries. The sex distribution at birth favoured males, with a ratio of 915 females to 1000 males (F:M). The sociodemographic profile of the parents and the obstetric history of the mother did not have any statistically significant impact on the birth weight of the newborn [Table 1].
Table 1.
Association of birth weight with sociodemographic profile of the parents and obstetric history of the mother
| Variable | Birthweight |
P | |
|---|---|---|---|
| <2.5 kg |
≥2.5 kg |
||
| n (%), N=46 | n (%), N=180 | ||
| Mother’s age (in years) | |||
| <18 years | 04 (40.0) | 06 (60.0) | 0.163 |
| 18−23 years | 25 (23.8) | 80 (76.2) | |
| 24−29 years | 12 (14.3) | 72 (85.7) | |
| ≥ 30 years | 05 (18.5) | 22 (81.5) | |
| Father’s age (in years) | |||
| <25 years | 08 (44.4) | 10 (55.6) | 0.051 |
| 26−30 years | 16 (20.8) | 61 (79.2) | |
| 31−35 years | 12 (15.2) | 67 (84.8) | |
| ≥ 36 years | 10 (19.2) | 42 (80.8) | |
| Mother’s education | |||
| Primary | 09 (31.0) | 20 (69.0) | 0.079 |
| High School | 20 (19.2) | 84 (80.8) | |
| Intermediate | 15 (24.2) | 47 (75.8) | |
| Graduate & post grad. | 02 (06.5) | 29 (93.5) | |
| Father’s education | |||
| Illiterate | 01 (25.0) | 03 (75.0) | 0.060 |
| Primary | 11 (22.4) | 38 (77.6) | |
| High School | 24 (26.6) | 66 (73.4) | |
| Intermediate | 07 (18.5) | 31 (81.5) | |
| Graduate & post grad. | 03 (06.7) | 42 (93.3) | |
| Father’s occupation | |||
| Business | 07 (16.6) | 35 (83.4) | 0.149 |
| Labourer | 27 (24.6) | 83 (75.4) | |
| Job/service | 02 (06.5) | 29 (93.6) | |
| Driver | 02 (14.3) | 12 (85.7) | |
| Farmer | 08 (27.6) | 21 (72.4) | |
| Gravidity | |||
| 1 | 16 (16.0) | 84 (84.0) | 0.433 |
| 2 | 20 (23.8) | 64 (76.2) | |
| 3 | 07 (21.2) | 26 (78.8) | |
| ≥ 4 | 03 (33.3) | 06 (66.7) | |
| Parity | |||
| 0 | 25 (20.1) | 99 (79.9) | 0.975 |
| 1 | 19 (20.9) | 72 (79.1) | |
| 2 | 02 (18.2) | 09 (81.8) | |
| Mode of delivery (present pregnancy) | |||
| NVD | 19 (26.7) | 52 (73.3) | 0.105 |
| LSCS | 27 (17.4) | 128 (82.6) | |
| Sex of child | |||
| Male | 25 (21.1) | 93 (78.9) | 0.745 |
| Female | 21 (19.4) | 87 (80.6) | |
There was no association between maternal weight gain or severity of anaemia across various trimesters of pregnancy and the birth weight of the child. Presence of anaemia in the third trimester was found to be significantly associated with birth weight of the newborn. Significant changes in birth weight were noted with alterations in hemoglobin concentrations, including absolute points of increase or decrease in the hemoglobin gram percent from the second to the third trimester and from the first to third trimester [Table 2].
Table 2.
Association of birth weight with change in mother’s body weight (in kg) (from her prepregnancy weight)
| Birth Weight |
P | ||
|---|---|---|---|
| < 2.5 kg n (%), N=46 |
≥2.5 kg n (%), N=180 |
||
| T1-T2 | |||
| More than 0.5 kg loss | 5 (33.3) | 10 (66.7) | 0.433 |
| Weight change between±0.5 kg | 04 (19.0) | 17 (81.0) | |
| Weight gain of more than 0.5 kg | 37 (19.5) | 153 (80.5) | |
| T2-T3 | |||
| Less than 3 kg weight gain | 14 (22.2) | 49 (77.8) | 0.824 |
| Weight gain between 3 and 5 kg | 19 (20.9) | 72 (79.1) | |
| Weight gain of more than 5 kg | 13 (18.1) | 59 (81.9) | |
| T1-T3 | |||
| Less than 5 kg gain | 14 (27.5) | 37 (72.5) | 0.357 |
| Weight gain between 5 and 10 kg | 26 (18.4) | 115 (81.6) | |
| Weight gain of more than 10 kg | 06 (17.6) | 28 (82.4) | |
| Anaemia (1st trimester) | |||
| Absent | 24 (21.4) | 88 (78.6) | 0.691 |
| Present | 22 (19.3) | 92 (80.7) | |
| Anaemia (2nd trimester) | |||
| Absent | 13 (22) | 46 (78) | 0.709 |
| Present | 33 (19.8) | 134 (80.2) | |
| Anaemia (3rd trimester) | |||
| Absent | 07 (11.3) | 55 (88.7) | 0.037 |
| Present | 39 (23.8) | 125 (76.2) | |
| Hb change: T1-T2 | |||
| −0.6 or more | 23 (19.5) | 95 (80.5) | 0.691 |
| −0.5 to 0.5 | 14 (19.2) | 59 (80.8) | |
| 0.6 or more | 09 (25.7) | 26 (74.3) | |
| Hb change: T2-T3 | |||
| 0.6 or more fall | 22 (34.4) | 42 (65.6) | 0.001 |
| −0.5 to 0.5 | 18 (19.4) | 75 (80.6) | |
| 0.6 or more | 06 (8.7) | 63 (91.3) | |
| Hb change: T1-T3 | |||
| 0.6 or more fall | 35 (28.7) | 87 (71.3) | 0.003 |
| −0.5 to 0.5 | 07 (10.4) | 60 (89.6) | |
| 0.6 or more rise | 04 (10.8) | 33 (89.2) | |
On comparing the mean change in hemoglobin across the trimesters, the mean hemoglobin change from the first to the third trimester was found to be different in the newborns with low birth weight and normal birth weight and the difference was statistically significant [Table 3 and Figure 1].
Table 3.
Comparison of change in mean hemoglobin with the birthweight of the newborn
| Birth weight <2.5 kg Mean (S.D.) | Birth weight ≥2.5 kg Mean (S.D.) | P | |
|---|---|---|---|
| Mean hemoglobin changes from 1st to 2nd trimester | −0.8 (1.4) | −0.8 (1.9) | 0.999 |
| Mean hemoglobin changes from 2nd to 3rd trimester | −0.3 (1.3) | 0.1 (1.2) | 0.003 |
| Mean hemoglobin changes from 1st to 3rd trimester | −1.4 (1.3) | −0.7 (1.4) | 0.009 |
Figure 1.
Comparison of change in hemoglobin across various trimesters, hb_t1_t2: Change in hemoglobin from 1st to 2nd trimester, hb_t2_t3: Change in hemoglobin from 2nd to 3rd trimester, hb_t1_t3: Change in hemoglobin from 1st to 3rd trimester
DISCUSSION
The analysis revealed that the absolute values of Hb and its associated severity of maternal anemia during various trimesters of pregnancy did not exert an impact on the birth weight of the child. Existing literature presents conflicting outcomes regarding the influence of absolute Hb levels on birth weight. For instance, Restrepo-Mesa et al.[11] found no discernible association between maternal anemia and low birth weight. Conversely, some studies suggest that variations in hemoglobin levels throughout pregnancy can affect plasma volume expansion, with reduced plasma volume potentially leading to an increased risk of low birth weight infants.[12]
Our study identified significant changes in birth weight associated with variations in hemoglobin concentrations between the second and third trimesters, as well as from the first to the third trimester. The timing of anaemia emerged as a crucial factor influencing low birth weight, likely due to reduced oxygen transport and insufficient iron reserves in early pregnancy.[13] These findings underscore the potential role of fluctuations in maternal hemoglobin levels during specific intervals of pregnancy in affecting birth weight. Systematic reviews have noted the impact of first trimester anaemia on birth weight but reported no significant effects of anaemia in the second or third trimesters.[13]
Considering a U-shaped curve to explain the effects of maternal hemoglobin on birth weight, highlighting that third-trimester anemia could improve birth weight.[14] The maternal iron status was found to be associated with the outcomes. An iron-replete status was found to be associated with higher oxidative stress leading to adverse birth outcomes. The differing outcomes are speculated to stem from a low baseline prevalence of anemia in the participants and high compliance with evidence-based interventions in anemia treatment. Extremely high maternal hemoglobin concentrations have been identified as a cause for impaired material exchange in the placenta due to inadequate volume expansion of the blood, higher blood viscosity, and hampered hemodynamic velocity. Moreover, extremely high hemoglobin concentrations may restrict blood movement and cause blood vessel blockage in the placenta. This creates an intrauterine environment of oxidative stress subsequently leading to intrauterine growth restriction.[15] It was observed in the current study that hemoglobin levels of the mother in the third trimester were significantly associated with the birth weight of the newborn in line with the proposed hypothesis.
Our study suggests that rather than focusing solely on absolute hemoglobin values, attention should be directed toward understanding the timing of changes in hemoglobin levels and the body’s response to these fluctuations. Further research is needed to determine the optimal timing for therapeutic interventions to minimize potential harm to the baby during these fluctuations.
The study assesses hemoglobin levels across all trimesters due to the early registration of most pregnant women at the health centre. Standardized questionnaires, use of a calibrated instrument and skilled and trained personnel conducting antenatal care examinations ensure the quality of data collected.
However, the study’s exclusion of unsuccessful pregnancy outcomes introduces potential selection bias, which limits the generalizability of findings. Moreover, the use of a standard World Health Organization criterion for anemia disregards gestational trimester variations, thereby impacting the accuracy of the prevalence assessment. The study fails to adjust for iron supplementation in pregnancy, which is a crucial factor influencing anemia outcomes. Furthermore, the exclusive measurement of hemoglobin levels without differentiation of anemia types or consideration of underlying causes limits a comprehensive understanding of anemia in the studied population.
CONCLUSION
This study highlights the importance of considering not only absolute Hb-levels but also the changes in maternal hemoglobin concentrations across trimesters when evaluating their impact on birth weight. The observed changes in birthweight with variations in hemoglobin concentrations suggest that the timing and trajectory of anemia during pregnancy are crucial factors. Future research focused on these dynamic aspects of maternal hemoglobin needs to be undertaken to refine treatment strategies, develop targeted interventions, and optimize outcomes for both mothers and newborns. Further investigation into the timing of therapeutic interventions and an intricate understanding of anemia’s role in pregnancy could lead to more effective management and improved birthweight outcomes.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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